One of the long-term goals in electronics technology has been to provide higher functionality at a lower cost, and in a more convenient package. Electronic data modules are no different. There is a constant struggle to increase memory capacity and access speed, while at the same time decreasing module cost and size. Similarly, manufacturers have struggled to identify a package which may be used without disrupting the utility of the apparatus in connection with which the data module is used. This has led to smaller data modules, and to a variety of unique casing designs. The innovations disclosed herein are believed to contribute to a major advance in this direction.
As a result of the aforementioned trend toward compactness, data modules have been constructed using integrated circuit technology, and using very small casings which provide contacts whereby such data modules may be accessed. Current modules, however, have not met commercial expectations, particularly in the areas of reliability, package utility and module life. Data often is lost or miscommunicated due to dead batteries, or to poor electrical connections within the module itself. Further, many data modules are unsuitable for inconspicuous mounting, and may be unsuitable for mounting at all. The data module disclosed in U.S. Pat. No. 4,982,371 to Bolan et al., for example, has many limiting features, including limitations related to the use of onboard battery power, to its coin-like package and to the abundance of electrical connections between module components.
Further, the Bolan module employs an onboard battery, the module life thus extending only as long as the battery life. Once the battery voltage deteriorates to a point that the memory loses data, the module is no longer useful. Because all batteries self discharge, it will be understood that failure of the module and a loss of the data contained therein will eventually result. Additionally, the rate of battery discharge may be accelerated by various factors, including the number of transactions that the module performs, the temperature, and the RAM memory size. Further, because batteries generally include hazardous materials such as lithium and mercury, the Bolan data module may be environmentally unsafe.
The casing of the Bolan module also is unsuitable, it being difficult to mount or attach the module to physical items. The Bolan module's casing, it will be noted, is divided into first and second casing halves. This two-part casing makes it difficult to "pot" internal components, a procedure often used to ensure that all electrical connections are secure. The Bolan module instead relies on an elastic conductive material which applies pressure to contact points on the first and second casing halves. Potting material must be kept clear of these contact points. This is accomplished by pouring potting material into one-half of the casing, and then fitting the other half of the casing over the first casing half. If too much potting material is poured into the first casing half, an open contact can result. If too little potting material is poured into the first casing half, the casing can be partially crushed during use. Also, potting material can surround the elastic conductive material, thus reducing the amount of pressure the elastic conductive material exerts on the contact points.